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I just learned about Gradle an hour ago. It reminds me of "Cradle to Grave" which I thought was a good name for Software Project Manager. After reading your question I googled it's meaning and in December 2011 the inventor said:

My original idea was to call it Cradle. The disadvantages of that name
were:

to diminutive

not very unique

As Gradle is using Groovy for the DSL I went down the G-road and
thought about calling it Gradle. Everyone I asked liked it so that
became the official name. That was about 4 years ago. I’m still very
happy with the name.

So from the author we can gleam the Gradle was invented in 2007.

More to the point

Gradle is an open-source build automation system that builds upon the
concepts of Apache Ant and Apache Maven and introduces a Groovy-based
domain-specific language (DSL) instead of the XML form used by Apache
Maven for declaring the project configuration.1 Gradle uses a
directed acyclic graph ("DAG") to determine the order in which tasks
can be run.

Gradle was designed for multi-project builds, which can grow to be
quite large. It supports incremental builds by intelligently
determining which parts of the build tree are up to date; any task
dependent only on those parts does not need to be re-executed.

The initial plugins are primarily focused on Java,2 Groovy and Scala
development and deployment, but more languages and project workflows
are on the roadmap.

In computer old school terms we can say it only compiles objects that have changed in a project when some source code has changed. Thereby saving total compile time from hours to minutes.

In layman's terms we can say it's a project manager that knows all the bits and pieces required to build something.